Fixes Issue 697

Alright, added in list stuff to the alien's New() to handle it, and while I was at it I reworked add_to_mob_list() to actually be useful and used that in some places instead (It just takes into account everything for the lists, so that should be a bit more robust.

git-svn-id: http://tgstation13.googlecode.com/svn/trunk@4203 316c924e-a436-60f5-8080-3fe189b3f50e

code/modules/mob/mob.dm

@@ -1,13 +1,10 @@
 /mob/Del()//This makes sure that mobs with clients/keys are not just deleted from the game.
 	ghostize(1)
 	remove_from_mob_list(src)
-	living_mob_list -= src
-	dead_mob_list -= src
 	..()
 
 /mob/New()
 	add_to_mob_list(src)
-	living_mob_list += src//No way this can possibly fail
 	..()
 
 /mob/proc/Cell()